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 Post subject: Re: Help w/ West H-122 conversion
PostPosted: Jul Sun 02, 2017 5:14 am 
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No it's clear enough. I have saved it in my files for the long winter months. 8)

How you say? It is in Photobucket, a .png file which I can save but not open. So I just took a screen shot, a pic of the laptop screen with my camera. 8)

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 Post subject: Re: Help w/ West H-122 conversion
PostPosted: Jul Sun 02, 2017 6:16 am 
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If you use Windows the picture should open.


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 Post subject: Re: Help w/ West H-122 conversion
PostPosted: Jul Mon 03, 2017 3:07 am 
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Win 10 tells me We can't open this file.
Using 'save as ...'
I get no choice as to type of file, then the pic is saved as a PNG file. I just tried it again. That's saving it from here, this thread.
(If I open PhotoBucket, forget it, can't save anything, just the link.)

But I have the schematic, and also it will be here for the near future at least. That looks interesting.

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 Post subject: Re: Help w/ West H-122 conversion
PostPosted: Jul Mon 03, 2017 3:37 am 
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Something isn't right with your computer then as I use Windows 10 and can open png files.

Both the photos app and Windows photo viewer will open it on my computer.

That said when I downloaded the schematic it was a lower resolution than the original schematic and any attempt to enlarge it to anything large enough to see the actual component values just made it blurry.


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 Post subject: Re: Help w/ West H-122 conversion
PostPosted: Jul Tue 04, 2017 3:34 pm 
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Apparently there was a Microsoft upgrade that caused a glitch in the viewer software.
Supposedly that was fixed, but in my case, the fix has not come thru. I guess.
As long as the upgrades help keep spybots away, I'm good with it all.

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 Post subject: Re: Help w/ West H-122 conversion
PostPosted: Jul Tue 04, 2017 6:02 pm 
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Oh ok did not know there was a glitch as I hadn't updated mine in quite some time.


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 Post subject: Re: Help w/ West H-122 conversion
PostPosted: May Fri 11, 2018 2:19 am 
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Finally back to this project. My son gave me the much abused Dahlberg Pillow Speaker radio for Xmas. When they announced they'd be visiting in April, I focused on resurrecting that so that my grandson could put dimes into it and hear it play. And play it did, with a CD Walkman jumpered to the volume pot. We had a patio party. 8)
Attachment:
Dahlby-D-2.jpg
Dahlby-D-2.jpg [ 103.37 KiB | Viewed 801 times ]


The Westinghouse Project.
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Scarface.jpg
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The "24 volt" doorbell transformer I was going to use has an unloaded output of only 17.3 volts, crap. It can't supply heater volts for the 25L6's.
So I've found something better, a good sized Hammond transformer with a 63 vac secondary. It will supply heaters of 4 tubes, the 25L6 X 2 plus 2 of the 6 volt tubes. The 6SA7 will be getting filament voltage from a small 6 volt transformer from my junk boxes. I don't think the pilot light will make the cut, maybe will use a 120 volt LED.
B+ will be isolated by the razor outlet transformer, reversed to lower the secondary voltage to 105 vac.
Well, I might try a higher B+ but want to hear some results first.

Thinking also about paint schemes for this one to cover up the big scar which will get glued and filled. I'm thinking a two-tone effect by leaving the grill bars natural, like black and tan. Or maybe candy apple red with gold grill bars and knobs. Maybe just a neutral Ivory.

The small transformer has an unloaded output of 7.3 vac. Using a guinea pig tube, a surplus 7H7 that draws 0.3 amps, for a test, voltage levels out at 6.5. So I'm adding a 1 ohm 5 Watt resistor for a perfect heater voltage of 6.2 vac. The transformer stayed cool for the duration, so will try a pilot lamp in parallel.

All speculation until I actually do the tests.
Edit: Rats, the 63 volt transformer just isn't up to supplying the load of four 300 milliamp tubes. I will carry on searching.


Attachments:
TrnsTest.jpg
TrnsTest.jpg [ 215.85 KiB | Viewed 783 times ]

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Wed 16, 2018 10:13 pm 
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My dream of fitting 3 transformers into the cabinet has been shattered. With a heater string of 4 tubes, 62 volts, the Hammond output dropped form 63 volts to about 7.
I tried a larger 65 volt transformer that powered up the heaters nicely but over the course of 20 minutes went from warm to almost too hot to touch, over 40 degrees Celsius.
I am now looking at a robust arrangement of two larger transformers from my junk box that are piggy backed to provide a 120 volt secondary, plus both a 6.7 volt and a 50 volt tap for the heaters.

The upshoot is, 25L6 tubes need a hefty power supply. My toy doorbell transformers might work, but I'd need 6 of them. :lol:


Attachments:
Transforming.jpg
Transforming.jpg [ 200.53 KiB | Viewed 778 times ]
Transfrmed.jpg
Transfrmed.jpg [ 204.74 KiB | Viewed 778 times ]

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Thu 17, 2018 1:03 am 
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I've done a bench test, jumpered the 25L6's and connected their filaments in series to the 50 volt winding, while heating 2 300 milliamp Loctals with the 6 volt winding. The transformers got warm but not hot, under 102 degrees F.
I will play it safe and keep the small 6 volt supply on the 6SC7. I have my power supply and can stick with the tubes that came with the radio. In fact, they all carry the Westinghouse label, so are likely originals from 1946.

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Thu 17, 2018 3:23 pm 
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That fits right in with some of my circuits/modifications... :mrgreen:

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Thu 17, 2018 5:26 pm 
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35Z5 wrote:
That fits right in with some of my circuits/modifications... :mrgreen:
I've messed with 50L6 circuits, and in fact, this power supply is from such a project, but this is my first time using the 300 milliamp tubes. They are much more .... demanding. :lol:
Back next week with an update.

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Thu 17, 2018 8:00 pm 
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westcoastjohn wrote:
35Z5 wrote:
That fits right in with some of my circuits/modifications... :mrgreen:
I've messed with 50L6 circuits, and in fact, this power supply is from such a project, but this is my first time using the 300 milliamp tubes. They are much more .... demanding. :lol:
Back next week with an update.

Ahhh, not a big deal, I have a Warco radio with 300 & 400ma tubes in same string... Of course it has a hot chassis, I don't worry over such... Daily player, probably has 5000 hours or more in this configuration...

Also a second Warco that uses a 43 in otherwise same string... I have installed a 6ZY5 in place of the 6J5, basing compatable with no changes... There are two 6ZY5 in the one with 43 but because of low current draw, I installed a jumper plug in one of 6J5 sockets for set with 6K6...

Image

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Fri 18, 2018 4:22 am 
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That's neat but I don't see a diode. Must be in the other side of the schemo. I am impressed with the simplicity of the design.

Speaking of hot chassis, I have my Zenith C-845 with the factory phono jack for a desk amp right now. The MP3 input is isolated with an audio transformer, so it is quite safe to use. But not ideal.
I am hoping this Westinghouse will take its place with a smaller footprint on the desk. And it will have complete isolation from household current. And I enjoy fooling around with tube circuits and trying to create a silk purse from a sow's ear, as they say. I'm eliminating the big dropping resistor.

I have two independent 6 volt windings now, so will be able to switch off the heater supply to the radio front end tubes, reducing current thru the power supply transformers by 600 milliamps. The first audio amp/inverter tube is on its own private filament supply, the small 7 volt transformer. Mostly, I will be streaming to the phono jack from my laptop or my cell phone on WiFi.

Why? Because of no good AM stations.
( Vancouver's best known DJ, Red Robinson, retired last year at 80. His former oldies AM radio station which I always tuned to when I repaired an AM radio, is now 24 hour sports talk. There is one other AM station I'd listen to, the CBC, but it comes in better on FM, same programming. )
So in this area, AM is good only for a whole house transmitter, a future project.

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Last edited by westcoastjohn on May Mon 21, 2018 9:36 pm, edited 1 time in total.

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Fri 18, 2018 5:01 am 
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Diode?? The two 6J5 are acting as halfwave rectifier, plate & grid tied together... Schematic has complete heater string with dropper cap, B+ & audio output circuitry... This set originally used a resistance line cord... Excepting for tubes, runs cool with no heat...

The 6K6 is somewhat audio challenged as B+ is approx half of recommended, still it plays louder than I need... I was determined to use original type tubes, Don(Bike & Swim)and I bounced ideas back and forth till the circuitry was finalized...

BTW I didn't draw RF circuitry as otherwise it's AA5...

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Mon 21, 2018 9:31 pm 
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Doh, I didn't notice the grids and plates tied together. :o
I have saved your schematic to my files, thanks.

Also saved the schematic in this thread, interesting.
viewtopic.php?f=12&t=339413&p=2847724#p2847724

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Sun 27, 2018 5:45 am 
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Hot dawg! I finally made time for this project, got all my trannys in a row, and installed the silicon diode and an experimental dropping R on the B+ line. I had to rewire the front end filament connections for parallel 6 volt and the 25L6's in series for 50 volts. New wiring is routed close to the chassis much as possible. To expedite the test, used small wire nuts on some of the transformer connections.

Powered it up for the first time, using the variac at about 80 vac for starters. I had tried once last year, but found the rectifier tube was dead.
Passed the initial smoke test, so applied more voltage and saw the power tubes glowing nicely.
The other tubes are metal and take a while to become warm to the touch.

I waited for warm up then turned on the B+ and heard static, beautiful static.
With a bit of fiddling, was tuning in AM stations. The speaker is in great shape and audio is bright and clear.

Now that I have confirmation, finally, will go ahead with replacing the remaining 12 or 13 wax caps, :x and build the custom base cabinet for the transformers. It will be attached with brackets to the chassis screws. I want to increase B+, about 105 vdc, so will decrease the dropping resistor from 47 ohms to maybe 22 ohms. Will try reversing my power transformers as well. I have forgotten if the output was higher that way so will try it.
A toggle switch at the power cord applies the filament voltage, so I can delay B+ with the radio switch Off. 8)

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Tue 29, 2018 4:07 am 
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The 25L6 can handle up to 200Vdc B+ on the plates so if you desire more output power you could run B+ at 200Vdc, 125Vdc on the screen grids then drop the voltage down further to what the tuner section requires.

Would possibly produce around 5 watts of audio.


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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Tue 29, 2018 3:28 pm 
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Ok, now that I'm creating a power supply cabinet, (note to self) leave room for a 200 volt B+ supply. :lol:

Well I guess a voltage doubler circuit would do it, but the issue I'm having is drawing too much current thru my cheezy transformers. The one supplying the 25L6 filaments is getting very warm after 3 hours of play. Raising B+ will increase the current draw even more.
I bypassed the iso transformers and used a suicide cord for B+. Disconnected all other loads. That helped, but not happy with this gradual heat buildup.

I have 50L6's and a 12SA7, will try those along with a modified tranny arrangement. The idea was to make the radio run cooler and safer.

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Tue 29, 2018 5:27 pm 
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The 50L6 would definitely work.

There are 12 volt versions of the 6 volt tubes.

So you would ditch the rectifier tube if not done already replacing it with a single diode.

You then wire all the tube heaters in series with the audio driver tube heater closest to ground.

That would require a power transformer with 140 volt secondary of at least 300mA current capability.

I wanted to do that to a Halicrafters S-38C, but couldn't find a proper 140 volt transformer.

An alternative is a 25.2 volt center tapped transformer with 100 volt secondary and use the 25L6 tubes.

That way you can use the voltage doubler for B+ to the output tubes then use a separate 1/2 wave rectifier for the B+ to the rest of the circuit so that you don't need a large dropping resistor in the B+ line. If you wanted to you could then keep the original tube rectifier for the B+ for the rest of the radio and use the doubler just for the output tubes.

All that is only necessary if the radio's volume doesn't go loud enough for you.


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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Tue 29, 2018 6:24 pm 
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Right, not likely I will need more power. The radio will sit on my desk and I wear a hearing aid on that side. :lol:
The +6" speaker sounds great, but I might try a horn tweeter with it. It can be in the transformer cabinet.

I have a 50 volt winding that is center tapped, but that is the transformer that is heating up too much, so it is at max output at 300 millimps, NFG.

Yes, I need one more 12 volt tube, either a 12SF7 or a 12SC7, to not make any mods to the circuit. Except some required filament circuit mods, Two 50L6 and two 12 volt tubes. Then tube #3, likely the 6SC7 audio/inverter, has his own 6 volt power. Should be less noise, too.

In the experimental stage here, I'll just sub in a 150 milliamp tube with alligator clips for a 124 volt filament line. I will use 3 tubes with the phono input, plus the ballast tube or a resistor.

Checking out some 50L6 tubes,
If I had a Tube tester, sold both junk ones I had, I could actually match them. The Admiral and Westinghouse on the right look to be from the same US manufacturer. The middle Westinghouse is Canadian made and is taller, sorry about that.
In the radio, I can compare cathode currents, maybe, if it ever gets to the tweaking stage. 8)


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